now OSS driver emulation -- and other drivers too -- works as well as OSS HW mode; block size error gone?

[Joerg-Cyril.Hoehle at t-systems.com]

Juan Lang wrote:
>> - Is there some central place in dsound for enforcing the 
>>invariant instead of identical code in the half dozen
>>OSS/ALSA/CoreAudio/Jack etc. drivers?
>No, or, not to my knowledge.

This is unfortunate.
Wine's dsound needs a channel back from winmm (which eventually calls
wineoss/winealsa etc. via wodOpen) to obtain the correct format data.
The OSS hardware mode does this (in wineoss.drv/audio.c) by updating
the supplied structure.  My patch does it for the OSS emulation mode.

However, testing on MS-Windows reveals that waveOutOpen() does not
modify the supplied WAVEFORMATEX structure.  Windows' wave*() seems to
completely ignore the incorrect nBlockAlign and nAvgBytesPerSample.
Apps can submit bogus data and still work.  So must Wine.

If Wine would not update the structure, there would be no channel back
to dsound.  So I'm wondering whether dsound/dsound.c can itself fix
the values.  Sadly I don't understand where the mapper and all these
adpcm/mp3/gsm drivers comes into play in dsound: Where can Wine set
  nBlockAlign == nChannels * wBitsPerSample/8 and
  nAvgBytesPerSec == nSamplesPerSec * nBlockAlign?
MSDN says in http://msdn.microsoft.com/en-us/library/bb669161(VS.85).aspx
"For non-PCM formats, this member must be computed according to the
manufacturer's specification for the format tag."
*Who* computes? The app? The mapper?

Note that msacm32.drv/wavemap.c:wodOpenHelper sets
 lpwfx->nBlockAlign and nAvgBytesPerSec
The line wodOpen:TRY: ... case MMSYSERR_NOERROR:
            wom->avgSpeedInner = wfx.nAvgBytesPerSec; goto found;
shows that nAvgBytesPerSec is considered an output variable after wodOpen().
The value need be correct, or crashes will likely follow.

In any case, I'm going to submit patches (in-place update) soon for OSS and
CoreAudio (ALSA later).  A cleaner solution is awaiting ideas.

Regards,
	Jörg Höhle
PS: While I've verified that MS-Windows' waveOutOpen does not modify the format
structure (given PCM), I've not tested what the dsound interface does.